1. Technical Field
The present disclosure relates to an automatic tilting vehicle that automatically tilts (self inclines) to the inside of a turn when turning.
2. Description of the Related Art
An automatic tilting vehicle has a vehicle tilting device, and the vehicle is automatically tilted to the inner side of a turn by the vehicle tilting device at the time of turning. For example, International Publication No. 2012/049724 describes an automatic tilting vehicle that includes a pair of front wheels (non-steered wheels) spaced laterally, a rear wheel (a steered wheel), a vehicle tilting device, and a control unit that controls the vehicle tilting device, and the pair of front wheels are rotatably supported by corresponding knuckles. The vehicle tilting device is a swing type vehicle tilting device and includes a swing member swingable about a swing axis extending in a longitudinal direction of the vehicle, a tilt actuator that swings the swing member about the swing axis, and a pair of tie rods. The pair of tie rods are integrally connected at the lower ends to the corresponding knuckles and pivotally connected at the upper ends to outer ends of the swing member on both lateral sides with respect to the swing axis. Each tie rod includes a shock absorber and a suspension spring.
When the swing member swings about the pivot axis, the pair of tie rods vertically move in opposite directions to each other, so that the front wheels move up and down in opposite directions relative to a vehicle body, thereby the vehicle inclines in a lateral direction. The control unit calculates a target tilt angle of the vehicle for stably turning the vehicle based on a steering operation amount of the driver and a vehicle speed and controls a swing angle of the swing member by the tilt actuator so as to tilt the vehicle so that a tilt angle of the vehicle conforms to the target tilt angle.
It is preferable that a tilt angle of the vehicle is controlled without delay in accordance with a driving operation of a driver. Consequently a target tilt angle of the vehicle is calculated, for example, so that a centrifugal force acting on the center of gravity of the vehicle based on a steering operation amount of the driver and a vehicle speed is estimated, and a resultant force of the estimated centrifugal force and the gravity acts in a predetermined direction. For example, a target lateral acceleration of the vehicle is calculated based on a steering operation amount of the driver and a vehicle speed, and a target tilt angle of the vehicle is calculated based on the ratio of the target lateral acceleration of the vehicle to the gravitational acceleration. It is also preferable that a steered angle of the rear wheel be controlled without delay in accordance with a driving operation of the driver. Therefore, for example, a target steered angle of the rear wheel is calculated based on a target lateral acceleration of the vehicle and a vehicle speed, and the steered angle of the rear wheel is controlled to be the target steered angle by a steering actuator.